The present invention relates to a device for signal path control for use in a motor vehicle and, more particularly, to a device which can be operated universally and bidirectionally with respect to signal paths and which permits a freely selectable change of input and output path assignments.
DE-A1-37 31 836 discloses an error diagnosis system for electronic units of a motor vehicle designed to receive error signals from electronic units and to display them. In this system, a vehicle contains at least one electronic unit, and preferably a plurality of electronic units, having self-diagnostic functions. Diagnostic outputs of the individual electronic units are connected to a plug-in connection to which a diagnostic tester can be connected. The data transmission from the plug-in connection to the diagnostic tester is made via lines connected in parallel. From each electronic unit capable of self-diagnosis, there is therefore a line connected via the plug-in connection to the diagnostic tester. In this known system, a undirectional data transmission is essentially provided.
If a large number of electronic units are to be monitored in a system as described in DE-A1-37 31 836 and a diagnosis device cannot be arranged near to the plug-in connection because, for example, it is to be served and read outside the vehicle, a multichannel connection from a vehicle interface to the diagnostic tester proves disadvantageous, for several reasons. When mechanically loaded, a correspondingly multiconductor cable tends to experience line breaks. In addition, cross-talk interference between different channels can occur. As a result, the advantages of such a device are greatly reduced.
DE-OS 33 33 333 discloses a method and a device for signal transmission in motor vehicle diagnostic devices. Measurement cables are fed to a peripheral which is protected against interference radiation. After amplification of the corresponding signals, they are preferably passed on to the diagnostic devices on a single optical path. No influencing of the signal assignment which can be controlled by at least one diagnosis device in a freely selectable way is provided.
DE-AS 11 48 763 discloses a compensation plotter for recording a multiplicity of measurement variable in which one of a multiplicity of measurement signals can be fed to the plotting amplifier of the compensation plotter via a two-stage arrangement of group switches. For this purpose, the corresponding switches are mechanically actuated at the input in accordance with the measurement value which is to be plotted at that moment.
DE-AS 25 04 102 discloses an arrangement for time-division-multiplex transmission of parallel analog measurement values and digital reports. This arrangement is suitable for a cyclical design of a serial data from corresponding to a multiplicity of signals present in each case in parallel. At the same time, individual groups of input lines are connected as appropriate, one after the other, to a parallel-serial converter by an executive sequencing control.
An object of the present invention is to provide a universal device for signal path control for use in a motor vehicle. The device of the present invention can be operated universally and bidirectionally with respect to signal paths and permits, in the course of the signal flow, a freely selectable change of the assignment of input to output path.
This object has been achieved in a device according to the present invention for signal path control having multi-gang switching components which are individually electrically driveable for switch actuation via p inputs, and single-gang switching components are individually electrically driveable via q further inputs. The device is assigned a drive circuit which comprises a shift register serially loadable via a loading input and having a transfer control input and an at least p+1 bit-wide parallel output; a bank of (p+q) latches having a common transfer input, in which bank the contents of (p+q) storage cells of the shift register can be loaded when the transfer input of the parallel output of the shift register is driven, and a logic unit connected upstream which is connected on the input side to a selection control line and to a transfer control line and whose output is connected to the transfer control input of the shift register, to the loading input of the shift register and to the transfer input of the bank of latches. The outputs of the latches are operatively connected to corresponding control terminals of the multi-gang switching components and single-gang switching components.
The device according to the invention for signal path control functions as a device for connecting a multiplicity of lines with serially provided signals to a single line, for example of a data cable, or vice versa.
In an advantageous manner, the selection of the signal path occurs by way of a serial path signal which is converted into a parallel drive bit pattern which corresponds to the desired signal path. A multiplicity of storage cells matched to the bit length of the serial signal permits the stationary signal path to be maintained until the signal path is correspondingly changed by the reception of a new serial path signal. In this manner, a cable with a minimum number of conductors is required between a data entry interface or data distribution interface and a data-receiving or data-transmitting system. At the same time, a high degree of interference signal suppression between different data channels is achieved.
Further advantages are provided by the present invention: For example, the device can accordingly be used both in a vehicle and also outside a vehicle. It is also particularly suitable as a component of an off-board diagnosis system.